Overload protective device.



H. A. STEEN.

OVERLOAD PROTECTIVE DEVICE.

APPLICATION HLED JULYZZ, 1911.

Patented Nov. 28, 1916.

'mgmi ,a.,%m 42% mom W marinara aysrnnrv, or iarnwnunrin, Wisconsin, assrenon. er MESNE assieninsure, 'ro ALLIS-CHALMERS mauuracrnnrne COMPANY, a coaronarron or nnnawann I meant):

To' all whom it may concern:

Be, it known that I, HALFDAN A. SrEnN, a subject of the King of Norway, residing at Milwaukee, in the county of Milwaukee and Sta-tent -Wisconsin, have invented certain new'and useful Improvements in Overload Protective Devices, of which the following is a full, clear, and exact specification.

My invention relates to control devices, such as protective devices, of the overload or other type, for alternating current circuits, and more particularly to the adjustment of such devices. In the operation of devices of this character the adjustment has I heretofore generally been obtained by varying the air gap of the device. This is often unsatisfactory, for many reasons.

It is the object of my present invention to eliminate this mechanical adjustment, and to provide an electrical adjustment instead. In attaining this object an additional coil is provided on the same magnetic circuit as the series coil of an overload protective or other device for alternating current circuits, and this additional coil is connected in a local circuit of variable resistance. This produces a current transformer, the main series coil being the primary and the additional coil the secondary. By varying the resistanceof the secondary circuit of this transformer, the flux produced by the passage of a given current through the primary is also varied. In consequence, the value of the current at which the device operates may be varied by adjusting the resistance of the circuit of the additional coil.

The various novel features of my inven tion will appear fromthe description and drawings, and will be particularly pointed out in the claims.

Figure 1 shows diagrammatically one embodiment of my invention; and Fig. 2 shows a modification.

The alternating current device to be protected, here shown as an alternating current generator 10, is connected to the alternating current circuit 11 through circuit-breaker 12, this circuit-break r g biased to open position but normally a in closed position by a latch 18. A coil 14 is connected so as to carry a current proportional to the current supplied by the generator 10; as shown,

the coil 14 is in series with such generator. The core 15 of the overload coil 14: may act Specification of Letters Patent. I

upon either act'r.

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' Patented Nov. as, r are.

Application filed July :22, 1911. Serial No. 639,989.

directly on the latch 13 of the circuitbrealrer, as shown in Fig. 1, or may control a switch 16 in the circuit of a coil 17 controlling such latch, shown in Fig. 2. The coil 1'! is shown as tripping coil and the switch 18 as normally open.-

On the same magnetic circuit as the coil 14.- is an additional coil 18. The coils M and 18 are preferably 30 wound relatively to each other that the magnetic leakage between the coils is as small as possible. This is indicated on the drawings position of one coil upon the other. The coil 18 is connected in a local circuit in which is a variable impedance 19; this impedance is illustrated as a simple rheostat.

The coils 1a and 18, with their common core 15, form a current transformer. F or a given current in the primary of such a transformer, the current in the secondary remains substantially constant regardless of the resistance of the secondary circuit. The effect of a variation in the resistance of the secondary circuit, the primary current remaining constant, is thus to vary in the same sense as such resistance variation the voltages across the terminals of the respective transformer coils and the flux in the transformer core. Thus for a given current in the machine 10, :2. n in the value of the resistance 1 s a variation in the produced in the core 5 will be raised when flux, and will thereor traversed by a cave are close the switcl 16 by the tripping coil 17, variation in the value of the r nce 19 will vary the value of the cur which circuitbreaker 12 is tripped. The ter the amount of the resistance 19 in 1., rcuit with the coil 18 the lower will be the ampere point of operation of the circuitl il Thus an easy and accurate mode at adj ment is provided.

My invention is capable of v-ci cation in detail, and I an such modification which cues not from the spirit and scope of my inventmn as set forth in the appended claims.

/V hat I claim as new is:

1. In an automatic circuitvice for alternating curren.

electromagnet comprising a winding carrying alternating current, an element of magnetic material disposed in inductive relation to said winding and movable in response to energization of said winding to a predetermined degree, a circuit-controlling device rendered operative through actuationof said element of magnetic materlal, and

means for var'yingthe value of current-in said Winding at which said element of magnetic material is actuated for circuit-controlling purposes, said meanscomprising a second winding permanently closed-circuited and in inductive relation to said first winding and said element of magnetic material, and a variable impedancein the. circuit of said second winding.

2. In a circuit-bremzing apparatus for alternating current circuits, controlling means responsive to abnormal conditions in the circuit to be controlled and comprising a winding carrying alternating current proportional to the current in the circuit to be controlled a movable member of magnetic material whose effective actuation is controlled by magnetic effects produced thereon by said winding, and means for varying the value of current in said winding at which said member is effectively actuated, said latter means comprising a Winding inductively related to said first winding andsaid memberlof magnetic material and permanently closed-circuited through a variable impedance during the use of the apparatus.

3. In a circuit-controlling apparatus, a switch, and means for controlling the operationfof said switch in response to abnormal conditions in the circuit to be controlled, said controlling means comprising an 0 erating coil carrying alternating current 0 an intensity proportional to that of the current in the circuit to be controlled, a member of magnetic material inductively related to said coil and actuatable in response to sufiiclent energizatlon of said coil, and means for I modifying the-effect of said coil on said member of magnetic material to variably adjust the value of current in said coil at which said member is'efi'ectively actuated, said means comprising a second coil inductively related to said first coil and said member of magnetic material and permanently closed-circuited through a varlable resistance.

4. In a circuit-controlling apparatus forv alternating current circuits, a controlling device responsive to abnormal conditions in the circuit to be controlled, said controlling device comprising an operating coil carrying alternating current proportional to the trolling device responsive to abnormal conditions of diiferent intensities in the circuit to be controlled, said controlling device comprising an operating winding carrying alternating currentof a value proportional to that of the currelitjn the circuit to be controlled, and a member of magnetic material 'actuatable under the influence oi the magnetic effects produced thereon by said winding, and means for calibrating said controlling device to render said device capable of effectively actuating said member of magnetic material on the occurrence of abnormal circuit conditions of difi'erent intensities,

said calibrating means comprising a shortcircuited winding inductively related to said first w nding and sald member of magnetic materlal, and regulable means associated with said second winding and operative to vary the effect of said second winding in opposing actuation of said member of magnetic material by said first winding.

6. In an automatic circuit-controlling device for alternating current circuits, an. electromagnet comprising a winding, and an element of magnetic material inductively related to said winding and movable in response to energization of said Winding to a predetermined degree, a controlling. member rendered operative through actuation of said element of magnetic material, and means for varying the value of alternating current in said Winding at which said element of magnetic material is actuated for effective circuitcontrolling purposes, said means comprising a second Winding inductively related to said first winding and said element of magnetic material and having its circuit of variable impedance and closed during the use of the apparatus.

,In testimony whereof I affix' my signature, in the presence of two witnesses.

HALFDAN A. STEEN.

Witnesses:

G. B. SCHLEY, CHAs. L. BYRON. 

